tests: disable COW checking by default, and enable it for specific tests
COW checking needs that all libraries are consistently compiled with asserts enabled. This is not the case for the Foundation overlay anymore.
Therefore it does not work with some tests which interop with Foundation.
The solution here is to disable COW checking by default, but enable it for Array tests which do not interop with Foundation.
(cherry picked from commit 0831240be65d1ec4a2ba3d4adb131aaf3740d88d)
(cherry picked from commit c13e5311cccc93b190ba98b2bef85882c9d760c8)